Abstract: An electronic imaging chip containing an array of photodiodes includes a multiplexed column buffer. The multiplexed column buffer serves a plurality of columns in the photodiode array. By multiplexing active amplifier elements, such as the differential gain amplifiers and the bus driver amplifiers, a wider area than one column width is available on the semiconductor chip for layout of the column buffer. In the disclosed embodiment, 4 columns share a common multiplexed column buffer. The area available for layout of the multiplexed column buffer is 4 times as wide as compared to that for a non-multiplexed column buffer.

Abstract: A semiconductor chip for forming an electronic image in a digital camera includes an offset canceling column buffer for use with active pixel sensors having a small electrical buffer amplifier within each pixel The active pixel sensors are arranged on a semiconductor chip with simultaneous access and reset lines. Each active pixel sensor includes an source follower current amplifier, which introduces small variations in offset voltage, causing pattern noise to be introduced into the output signal of the sensed image. A method and apparatus is disclosed for addressing an array of active pixel sensors in a sequence coordinated with a column buffer for canceling pattern noise. To cancel pattern noise, the current row N in the APS cell array is accessed and sampled. Next, the following row N+1 is accessed thereby resetting the current row. Finally, the previous row N in the APS cell array is accessed a second time and sampled.